Cellular mechanisms in antibody formation: To investigate, by transfer of lymph node cells and by a number of newly developed technics (enrichment of rosette forming cells, electron microscopy of isolated rosette and plaque forming cells, antibody producing cells induced in simple test tube culture) a number of the mechanisms involved in the cynthesis of antibody: induction of antibody formation (AF) by soluble products of phagocytic digestion of antigens; recruitment of antibody forming cells by a transforming DNA from active lymph nodes; relation of cells giving cell-mediated responses and antibody forming cells; cell- interactions in AR, both macrophage-lymphocyte and lymphocyte-lymphocyte; relations between antibody producing lymphocyte and plasma cell; and secretion of aftibody through the lymphocyte cell-wall. Transplantation immunology - antibodies: To confirm and extend recent indications of roles of alloantibodies in both the rejection and the enhancement of skin allografts in the mouse, by the application of rabbit anti mouse IgG1 to preparations of such antibodies; to examine these effects in relation to the natural mechanisms of allograft rejection; to extend these to attempts to identify an analogous immunoglobulin effector mechanism in the graft vs. host or runting phenomenon; and to study the mechanism of injury to allogeneic cells by this rejecting antibody. Transplantation immunology - antigens: To extend observations on a newly developed dialyzable form of BALB/c histocompatibility antigen, which retains HCA specificity; to compare this with analogous preparation from normal spleen cells of other mouse strains, and with similar preparations from tumor cells of some of these strains; to examine human (HLA) material for analogous forms of HCA.